1. Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
2. HSD University of Applied Sciences, Waidmarkt 3 and 9, 50676 Cologne, Germany
3. Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20251 Hamburg, Germany
4. Duke University, Pratt School of Engineering, FCiemas Building, 101 Science Dr., Durham, NC 27708-0271, USA